I don't know much about electrical terms and practice. Maybe someone can help me clear this out. I have helm manual. It mentions alot in many sections, where u have to do a self diagnostic on switches or connectors or terminals, about 'checking for a continuity'. Can someone pls explain it? What do u have to do to do this? what tool do i need? What indicates that there is a continuity? And what can u see if there is no continuity?

A piece of wire has electrical continuity between its two ends (it is electrically "continuous"). If you then cut the wire, there is no longer electrical continuity between the original two ends. "Checking for continuity" means checking to see if there is an electrical connection between two points. If a wire has come loose or something between the two points, then we say there is no continuity or there is an "open circuit" -- there is no electrical connection.

The best way to check for continuity on a circuit that is not electrically "live" is to use the resistance (ohms) measurement section of a digital multimeter or DMM. If there is an electrical connection or continuity between the two DMM probes, then the DMM will indicate a low resistance very close to zero ohms. If there is no continuity, then the DMM will indicate very high resistance or some (like mine) will simply not give a reading since the resistance is too high for it to measure. Some DMMs will have a "continuity check" setting where the DMM will beep when there is continuity between whatever you have the probes connected to, but I've only seen this feature on more expensive DMMs. You can pick up a perfectly good DMM for $15-$20 from Wal-Mart, Home Depot, etc.

Some electrical troubleshooting texts might mention using a "test light" type of device to check for electrical continuity. I would recommend that you use a DMM rather than test light devices on your vehicle circuits. And a DMM can be useful for other things anyway, such as using "DC voltage" setting to check for voltages in your car's wiring or using the "AC voltage" setting you can check electrical sockets in your home. And again, make sure there is no power in a circuit before you measure resistance with a DMM.

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Some electrical circuits are impossible to test without using a test light or constant power through a DMM. For example - let's say you wanted to know if you were getting power to your foggies. Clip one end of the test light to the chasis which in turn is hooked to the negative terminal of the battery, and the other to the feed from the fogs. By tapping into various points along the circuit, you can determine where the short is.

Or you can use the "DC voltage" setting on the DMM to do the same thing since a test light (in your example) does nothing more than indicate that voltage exists. The reason I recommend the DMM over the test light is because while both can indicate the presence (or absence) of voltage or continuity, the DMM does so at a very small fraction of the test light's current. This is no big deal for testing things like foggies, but when I'm probing my ECU or ABS controller, I'd prefer to keep the currents as low as possible.

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Originally posted by crashandburn Or you can use the "DC voltage" setting on the DMM to do the same thing since a test light (in your example) does nothing more than indicate that voltage exists. The reason I recommend the DMM over the test light is because while both can indicate the presence (or absence) of voltage or continuity, the DMM does so at a very small fraction of the test light's current. This is no big deal for testing things like foggies, but when I'm probing my ECU or ABS controller, I'd prefer to keep the currents as low as possible.

that and with the testlight if u dont know what your testing it could be an airbag wire and the testlight will trigger the airbag to go off

Originally posted by crashandburn Or you can use the "DC voltage" setting on the DMM to do the same thing since a test light (in your example) does nothing more than indicate that voltage exists. The reason I recommend the DMM over the test light is because while both can indicate the presence (or absence) of voltage or continuity, the DMM does so at a very small fraction of the test light's current. This is no big deal for testing things like foggies, but when I'm probing my ECU or ABS controller, I'd prefer to keep the currents as low as possible.

Agreed - a test light should be only used for testing - well lights. But there are advantages - first - it lights up - sometimes it's hard to read a meter in the dark, it has a built in fuse and I'd much rather blow that then my DMM (especially if it's expensive), and it clips on to the chasis really easily freeing up a hand to do whatever (pocket pool anyone? )

Originally posted by 5Gen_Prelude ...But there are advantages - first - it lights up - sometimes it's hard to read a meter in the dark...

This is very true, also when you're crawling around under your dash. That's why it's nice to have a DMM with the continuity tone function so you can hear it. The tone won't indicate voltage, but with a little creativity you can still make it work for many situations. For example, if you're looking for a short to ground in a wire, then you just check for continuity between the chassis and various points along the wire.

It's been a long time since I've really looked at any of the DMMs that are available now -- maybe you CAN get the continuity tone on a not-so-expensive model now? Hmmm, maybe I need to go shopping...

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